Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The question took on new significance recently when a doctor alerted federal regulatory agencies that a Colorado man who ate at least two bags every night for several years had “significant lung disease” similar to that seen in some microwave popcorn workers.

The illness — the first suspected case in a consumer — was linked to the man’s habit of inhaling fumes from extra-buttery microwave popcorn, which contains the chemical diacetyl. The additive gives foods a buttery taste and has been linked to severe lung disease in some microwave popcorn and flavor plant workers.

Dr. Cecile Rose, the lung specialist who examined the 53-year-old furniture salesman, says it “looks like a possible case, but we can’t be sure.” In her letter to federal officials, she said though it’s hard to make a causal connection, “we have no other plausible explanation.”

Rose says eating microwave popcorn isn’t dangerous, but what’s not yet known is what hazards may be associated with the fumes.

“My children continue to eat microwave popcorn every now and then,” says Rose, of the National Jewish Medical and Research Center in Denver. “I would probably urge that people not do it in a way that they are deeply inhaling the fumes.”

Dr. Phil Harber, a UCLA lung specialist, also says there isn’t enough information to determine whether there’s a “medically significant risk” but said people who eat lots of this kind of microwave popcorn should try to limit exposure when cooking it.

Some major microwave popcorn makers have already made the issue moot: They have eliminated or plan to drop the chemical from their recipes.

Meanwhile, a long-awaited government study that looks at chemical fumes emitted from microwaving popcorn at home — including those from diacetyl — will be published in a scientific journal in December.

The study, conducted by the U.S. Environmental Protection Agency, took nearly three years and was completed in 2006, according to Suzanne Ackerman, an agency spokeswoman.

Some critics have questioned the time lag in making the results public as well as the EPA’s decision to share the findings first with popcorn makers. Ackerman says the companies were permitted to read the report last year to make sure no competitive secrets were released.

“That was the only reason,” she says, noting that the researcher couldn’t get access to their ingredients without agreeing to those terms. “They were not allowed input into the final paper and they could not change a word of the paper — unless she (the researcher) had revealed a secret formula.”

Ackerman also says peer reviews and a rejection by a journal also delayed release of the results.

More than 45 chemicals were reportedly emitted during the popping and opening up of the popcorn bags.

Ackerman says the research looks only at the levels of fumes.

“We’re not going to know by this study if it harms anyone,” she says. “All it does is measure emissions.”